Funding for this research was provided by:
the National Natural Science Foundation of China (71173116)
the National Bureau of Statistics of China (2014ly046)
the Social Science Foundation of Jiangsu, China (2012JDXM012)
the Innovation Project of Universities’ Philosophy and Social Science in Jiangsu, China (2015ZSTD006)
the China Institute for Manufacture Developing, Nanjing University of Information Science and Technology, China (SK20140090-21)